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Practice with Our Flashcards or Watch the Video for Better Understanding

Simplifying Addition: Mastering the Art of Grouping by 10s and 100s

To help you master this technique, we have created flashcards and a practice video. These resources are designed to make practicing this addition method both fun and effective. Download our flashcards or watch the practice video to test your skills further.

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Breaking Down Addition Problems with Grouping

Understanding the Method

Addition problems can sometimes seem daunting, especially with larger numbers. The trick to making them more manageable is to group numbers into round figures—multiples of ten or a hundred. Let's break down this method using some examples.


Example 1: 63 + 427

  1. Initial Setup: We start with the problem 63 + 427. It looks complex, but we can simplify it by adjusting these numbers to round figures.

  2. Rounding the Numbers: To make 63 a round number, we need to subtract 3 (making it 60). If we add those 3 to 427, it becomes 430.

  3. Simplified Calculation: Now, the problem transforms into 60 + 430. This is much easier to handle and can be calculated mentally to get 490.

Example 2: 275 + 595

  1. Breaking It Down: Here, we start with 275 + 595. To simplify, we break 275 into 270 + 5.

  2. Adjusting and Rounding: We then add the 5 to 595, making it 600. The new problem is 270 + 600.

  3. Easy Addition: This simplifies the calculation to a straightforward mental math problem, resulting in 870.

Example 3: 51 + 83

  1. Initial Problem: We start with 51 + 83. By increasing 83 by 1 to make it 84, we need to decrease 51 by 1, resulting in 50.

  2. Simplified Addition: This changes the problem to 50 + 84, which is easier to compute as 134.

Example 4: 138 + 710

  1. Adjusting Numbers: Starting with 138 + 710, we subtract 10 from 710 (making it 700) and add that 10 to 138 (making it 148).

  2. Final Calculation: The problem simplifies to 148 + 700, resulting in an easy mental calculation of 848.


Key Concept:

By adjusting one number up and the other down by the same amount, we simplify the problem without changing the overall value.

One of the best resources for learning addition techniques is Khan Academy. They offer excellent explanations on various math topics, including how to simplify addition problems by grouping numbers into tens and hundreds. You can find their comprehensive video lesson on this topic here.

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